(a) Field of the Invention
The present invention relates to an automatic transmission for a vehicle, and more particularly, to a planetary gear train of an automatic transmission for a vehicle that improves a power delivery performance and enhances fuel consumption by implementing at least forward ten-speed with a minimal configuration and that reduces running noise of the vehicle by using a driving point in a low rotation speed range of an engine.
(b) Description of the Related Art
In general, in an automatic transmission field, research has been conducted regarding a multistage of a gear shift stage to enhance fuel consumption of a vehicle and to maximize drivability thereof, and recently, increase of an oil price is triggering a competition in enhancing fuel consumption of the vehicle. Accordingly, research regarding the reduction of a weight of an engine and that enhances fuel consumption thereof has been conducted for downsizing the engine, and in the automatic transmission, a research on technology that can simultaneously secure drivability and fuel consumption competitive power through a multistage of a gear shift stage has been conducted.
However, in the automatic transmission, as a gear shift stage increases, the internal component number, particularly, the planetary gear set number increases and thus a full length of the transmission increases and a mounting ability, a production cost, a weight, and power delivery efficiency may thus be worsened. Therefore, in the automatic transmission, to increase a fuel consumption enhancement effect through a multistage of a gear shift stage, development of a planetary gear train that can induce maximum efficiency with minimal number of components is important.
Accordingly, an automatic transmission is formed to implement a shift of 8-speed or more to be mounted within a vehicle, and research and development of a planetary gear train capable of implementing a gear shift stage of 8-speed or more has been continuously required. However, a general 8-speed or more of automatic transmission is often formed with three or four planetary gear sets and five or six control elements (friction element), and thus, a full length of the system increases and thus there is a drawback in that a mounting ability is worsened. Accordingly, to form a gear shift stage of an automatic transmission in a multistage, a double row structure that disposes a planetary gear set on a planetary gear set has been adapted or a dog clutch has been applied instead of a wet control element. However, such a structure is limited and a shift feel is worsened due to application of the dog clutch.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.